Microbiology, 2021

CHAPTER 11
Mechanisms of Microbial
Genetics
Figure 11.1 Escherichia coli (left) may not appear to have much in common with an elephant (right), but the
genetic blueprints for these vastly different organisms are both encoded in DNA. (credit left: modification of work by
NIAID; credit right: modification of work by Tom Lubbock)
Chapter Outline
11.1 The Functions of Genetic Material
11.2 DNA Replication
11.3 RNA Transcription
11.4 Protein Synthesis (Translation)
11.5 Mutations
11.6 How Asexual Prokaryotes Achieve Genetic Diversity
11.7 Gene Regulation: Operon Theory
INTRODUCTION In 1954, French scientist and future Nobel laureate Jacques Monod (1910–1976) famously
said, “What is true in E. coli is true in the elephant,” suggesting that the biochemistry of life was maintained
throughout evolution and is shared in all forms of known life. Since Monod’s famous statement, we have
learned a great deal about the mechanisms of gene regulation, expression, and replication in living cells. All
cells use DNA for information storage, share the same genetic code, and use similar mechanisms to replicate
and express it. Although many aspects of genetics are universally shared, variations do exist among
contemporary genetic systems. We now know that within the shared overall theme of the genetic mechanism,
there are significant differences among the three domains of life: Eukarya, Archaea, and Bacteria. Additionally,
viruses, cellular parasites but not themselves living cells, show dramatic variation in their genetic material and
the replication and gene expression processes. Some of these differences have allowed us to engineer clinical
tools such as antibiotics and antiviral drugs that specifically inhibit the reproduction of pathogens yet are